Television and Home Theater

had to re-post quest. have a 50in. hitachi projection, getting sound but no picture, after looking over some of the other forum questions, i played a dvd, and got a picture, for a little bit, then pushed a button and now nothing! any thoughts?!?!

I have a panasonic PT47X64 CRT rear projection. My picture is zoomed in and cannot be adjusted. I went through convergence and couldnt fix it. I also went through the aspect ratio options, no luck.
I also have the same problem with other inputs, so I dont think its the cable.
There is also a zoom function but i cannot access it.
sombody please help, or point me in the right direction.

The sound and picture on my tv work fine when I view high defintion content using the composite inputs and a Microsoft Xbox hooked up to them. However I cannot view anything hooked up to the coaxial input or component inputs. The high defintion inputs will also not display anything that is not high defintion. Through all of this the sound works perfect though. Seems that only HD digital signals will display, everything else is a no go...